Light emitting diodes (LEDs) are expected to the source of light for the next generation lighting which will replace incandescent bulbs and fluorescent lights. One conventional LED chip is illustrated in FIG. 1. The convention LED chip 10 includes a substrate 101. A P type layer 102 is formed on the substrate 101, and an N type layer 103 is further formed on the P type layer 102. Then, a passivation layer 105 is formed on two ends of the N type layer 103, and an N type contact pad 104 is formed on the N type layer 103. A terminal contact 106 is formed below the substrate 101. Therefore, the emitting surface 107 is formed on the upper surface of the N type layer 103.
Another conventional LED chip is illustrated in FIG. 2. The convention LED chip 20 includes a substrate 201 (for example made of sapphire). An N type layer 202 is formed on the substrate 201 while a reflector 209 is formed below the substrate 201. An N type contact pad 203 and a P type layer 205 are formed on the N type layer 202, such that a light emitting layer 204 is formed between the N type layer 202 and the P type layer 205. A transparent contact layer 206 is formed on the P type layer 205, and a P type contact pad 207 is formed on transparent contact layer 206. Furthermore, a protection layer 208 covers the outer surface of the N type layer 202, the P type layer 205, the light emitting layer 204 and the transparent contact layer 206 except the P type contact pad 207.
The aforementioned conventional LED chips still suffer some problems. For example, the contact pads 104 and 207 on the LED chips reduce the light emitting area and the light output, and the heat generated in the PN junction cannot be conducted outwards. Accordingly, there is still a need for a new LED chip to solve aforementioned problems.